Sheet metal material made from AA6xxx aluminium alloys are used in cars in the body and for body attachments (doors, tailgates, bonnets, etc.). The alloys which are usually used, such as, for example, AA6016 or AA6014, show both a good formability in the delivered state (T4) and a significant increase in strength after the paint baking cycle, for example in the case of a cathodic dip painting. The sheet metal material is solution annealed in the T4 state. For components in the visible region, the so-called outer skin parts, a good surface appearance, i.e. a quality with little or no roping, is a further requirement that the aluminium alloys are used.
For components having high requirements on the formability, aluminium materials are available on the market which are optimised with respect to formability and at the same time can be used for outer skin parts. However, even these metal sheets which are optimised with respect to formability cannot solve new requirements on the formability. Presently, due to the weight saving potential of aluminium, aluminium solutions are sought after for outer skin components which could not be produced previously from aluminium. For example, large-surface side wall parts of a motor vehicle are produced as a single-part component from a single aluminium alloy metal sheet. Such large-surface components could not be produced previously due to the limited formability of the aluminium material. Due to the lack of aluminium solutions, these large-surface body components are either produced from steel or the component is designed as a multi-part aluminium component, which leads to an increased effort in production due to additional joining steps.
The applicant has developed a material which fulfils very high requirements on the formability and is distinguished by high strain values in the T4 state. This aluminium composite material has already been referred to in international patent application WO 2013/037918 A1. The production method of the material indeed targets a maximum formability of the material, however in practice roping effects were visible which are caused by production.